Disk drives are widely used in computers, consumer electronics and data processing systems for storing information in digital form. The disk drive typically includes one or more head suspension assemblies and one or more storage disks. Each head suspension assembly includes a slider having an air bearing surface, and a read/write head that transfers information to and from the storage disk. Each storage disk typically includes a storage surface on each side of the storage disk. The storage surfaces are divided into a plurality of tracks that store data and/or other information used by the disk drive during operation.
The need to reduce data access times has led to increasing the rotational speed of the storage disks. Because of the increased speed, the rotating storage disks can generate significant air turbulence within the disk drive. Increased air turbulence can lead to unwanted vibration of the storage disks. For example, air turbulence can generate regions of low pressure near the storage disks, which are then filled by air rushing in because of the pressure differential. This repeated cycle causes chaotic and random flutter or wobble of the storage disks, resulting in disk vibration track misregistration (TMR).
In addition, in order to increase storage capacity, storage disks are being manufactured with increased track density, i.e. more tracks per inch. In conventional disk drives, each slider rides on an air bearing generated by rotation of the storage disk. The separation between the slider and the disk surface during rotation of the storage disk is referred to as the fly height. As track density increases, the fly height must necessarily decrease in order to maintain accuracy of the disk drive. Currently, fly heights can be on the order of 5 nanometers or less. A drawback of such low fly heights is that even slight vibration or imbalance of the storage disk can cause the slider to crash into the storage disk, resulting in loss of data and damage to the slider and/or damage to the storage disk.
Attempts to reduce vibration of the storage disk include manufacturing storage disks having greater thicknesses. However, a thicker disk can cause track misregistration due to the kinematic properties of the disk. More specifically, it is understood that in a comparison of two disks with different thicknesses, each having the same vibration amplitude, kinematic head-to-track offset during vibration has a direct correlation to the thickness of the storage disk. On the other hand, it is also acknowledged that a thinner disk is generally more susceptible to having a greater vibration amplitude, which typically results in an increase in the extent of track misregistration.